Light-emitting element and illumination device

Abstract

A light-emitting element includes: a phosphor layer including phosphor (phosphor particles) of at least one type; a substrate which has a thermal conductivity higher than a thermal conductivity of the phosphor layer, the substrate having a principal surface above which the phosphor layer is disposed; and a joining part which is interposed between the phosphor layer and the substrate to join the phosphor layer and the substrate together with metal. An adhesion layer and a reflecting layer are interposed between the joining part and the phosphor layer, the adhesion layer being light-transmissive and on a principal surface of the phosphor layer which faces the substrate, the reflecting layer being on a principal surface of the adhesion layer which faces the substrate.

1 . A light-emitting element, comprising:
 a phosphor layer including phosphor of at least one type;   a substrate which has a thermal conductivity higher than a thermal conductivity of the phosphor layer, the substrate having a principal surface above which the phosphor layer is disposed; and   a joining part which is interposed between the phosphor layer and the substrate to join the phosphor layer and the substrate together with metal,   wherein an adhesion layer and a reflecting layer are interposed between the joining part and the phosphor layer, the adhesion layer being light-transmissive and on a principal surface of the phosphor layer which faces the substrate, the reflecting layer being on a principal surface of the adhesion layer which faces the substrate.   
     
     
         2 . The light-emitting element according to  claim 1 ,
 wherein the joining part includes:   a first electrode layer which is on the principal surface of the substrate;   a second electrode layer which is on a principal surface of the reflecting layer which faces the substrate; and   a metal joining layer which is interposed between the first electrode layer and the second electrode layer to join the first electrode layer and the second electrode layer together.   
     
     
         3 . The light-emitting element according to  claim 1 ,
 wherein the joining part comprises sintered silver nanoparticles.   
     
     
         4 . The light-emitting element according to  claim 1 ,
 wherein the phosphor is disposed on a side of the phosphor layer which is closer to the substrate.   
     
     
         5 . The light-emitting element according to  claim 1 ,
 wherein the adhesion layer comprises a metallic oxide.   
     
     
         6 . The light-emitting element according to  claim 1 ,
 wherein a through hole penetrates through the substrate, the joining part, the reflecting layer, and the adhesion layer to extend continuously in a direction intersecting with the principal surface of the substrate, and   the through hole serves as an optical path for excitation light which enters from a substrate side of the light-emitting element to excite the phosphor.   
     
     
         7 . The light-emitting element according to  claim 1 ,
 wherein a diffusion layer which diffuses light is interposed between the phosphor layer and the reflecting layer.   
     
     
         8 . The light-emitting element according to  claim 1 ,
 wherein a surface of the phosphor layer which is opposite to the principal surface of the phosphor layer facing the substrate includes a region which is to be irradiated with the excitation light for exciting the phosphor, the region having a surface roughness with a wavelength greater than or equal to a wavelength of the excitation light.   
     
     
         9 . The light-emitting element according to  claim 1 ,
 wherein the principal surface of the phosphor layer which faces the substrate includes a region which is to be irradiated with the excitation light for exciting the phosphor, the region having a surface roughness with a wavelength greater than or equal to a wavelength of the excitation light.   
     
     
         10 . An illumination device, comprising:
 the light-emitting element according to  claim 1 ; and   a light source which emits excitation light for exciting the phosphor of the light-emitting element.